Treatment of still residue



Patented Nov. 1, 1938 UNITED STATES TREATMENT or STILL RESIDUE irank W.Corkery,

Grafton, Pa., assignor to Pennsylvania Industrial Chemical Corporation,a corporation of Pennsylvania No Drawing. Application January 12, 1937,Serial No. 120,192

4 Claims.

This invention relates to the purifying treatment of still residues of aparticular sort, and to the further treatment of such still residues toproduce a primarily elastic mass particularly 5 suitable for use inlinoleum, mastic tile,,and the like products. This constitutes acontinuation in part of my copending application Serial No.

v, 88,591, filed July 2, 1936, and also bears a species relationship tothe invention generically dislO closed and claimed in my co-pendingapplication 1 Serial No. 53,213, filed December 6, 1935.

The still residue with which I deal is a still residue remaining fromthe treatment of cokeoven light oil. This still residue containspolymers of resin-forming bodies in various stages of polymerization,heavy monomers, naphthalene, and varying percentages of solvents andsulphonates. It is a dark, viscous, oily substance, deficient in dryingqualities, and of itself possessing but little utility in the arts. Asit is commercially available, the still residue may be obtained fromeither of the following operations conducted upon the light oil derivedfrom the gases which are evolved in the coking distillation of coal.

One such source is the still in which cokeoven light oil is purified andfractionated to give crude benzol, crude toluol, No. 1 crude solventnaphtha (crude xylol), and No. 2 crude solvent naphtha. The residuumfrom this fractionation consists largely of heat polymers, and is knownin the trade as crude still residue. 'The fractions from the crudestill, after washing with sulphuricacid and neutralization, aredistilled in what are known in the trade as pure stills.

The residues from the distillation of these fractions comprise primarilyacid polymers and heat polymers, and comprise also sulphonates. It alsocontains sulphates from acid purification and neutralization which havenot been wholly removed by washing. This "pure still residue normally ismixed in a residue tank with the crude still residue, so that ascommercially available still residue contains at least the residualproducts from these two types of still dealing with coke-oven light oiland its fractions.

Usually'there is also mixed inwith these two still residues in theresidue tank a third residue which comprises bottoms from thedistillation of the heavier cuts of No. 1 and No. 2 crude solventnaphtha. Usually the still residue mixture is subjected to adistillation for the removal of solvents and naphthalene. Ascommercially available, however, the still residue yet contains a 5small indeterminate percentage of solvents and naphthalene. Althoughthere is variation in the above-noted practice in different cokingplants, commercial still residueusually consists of to crude stillresidue, or crude still residue and bottoms, and 25 to 30% pure stillresidue.

In preparation for an oxidizing treatment. or in preparation for otheruses of the still residue, I desirably remove sulphonates. Thissulphonateremoval I effect by commingling the still residue with apetroleum distillate, such as petroleum in naphtha, mineral spirits,kerosene, ligroin, gasoline, andthe like, in which sulphates andsulphonates are relatively insoluble. The sulphates and sulphonates maybe considered in practical eiTect wholly insoluble in these petroleumdistill6 lates at temperatures not exceeding and I therefore preferablymaintain the solvent mixture at or below such temperature. The use. ofany substantial quantity of any one of the petroleum distillates isuseful in the removal of 20 sulphates andsulphonates, but I prefer toutilize a volume of petroleum distillate almost double the volume of thestill residue, and prefer to use petroleum naphtha, which has the leastsolvent power 'for sulphates and sulphonates. In the ad- 25 mixture,the. other components of the still residue are soluble in the petroleumdistillate, but upon standing the sulphates and sulphonates settle out.Physical separation of the still residue solu-v tion and the sulphateand sulphonate precipitate 30 may be efiected in any suitable manner,as, for instance, by decantationor by filtration. Desirably, thesolution, after separation of the precipitate, is agitated, with a smallquantity of sodium hypochlorite, followed by a sodium hydroxide wash andwater washing, this latter treatment having the effect of improving theodor of the still residue.

I may then desirably introduce into the solution bleaching clay of anyof the well-known 40 sorts, desirably in a weight of from 2 to 5% theWeight of the solution, agitate it in the solution, and filter it out.The clay, as filtered from the solution, takes withyit some of thecolor-forming bpdiesof the still residue, leaving the solution im- 45proved in color as well as odor, and containing a lessened content ofimpurities. Following such of these purification steps as are employed,-I separate the petroleum distillate solvent and the still residue bydistilling off the petroleum solvent 50 either under vacuum or bystraight distillation.

Preponderantly, sulphates and sulphonates are found in the pure stillresidue, so their presence in the commercial still residue followsroughly the percentage of pure still residue to crude still 5 V residue,

" sider a still residue containing no substantial content of sulphatesand sulphonates to be our starting material, whether they be removed inby the process above desome manner, such as be initially present inscribed, or whether they negligible proportion.

Purification changes the character of the normal commercial stillresidue in several particulars. By purification the color of the stillresidue is changed from a dull, dark red to a bright.

yellowish red. The purified product lacks the sweetish odor associatedwith unpurified still residue, while retaining the characteristiccoal-tar odor and the burnt odor typical of still residue.

The voscosity of purified still residue is much lower than that of astill residue before purification. As typical, I have noted a lesseningin visout precipitation cosity from 180 Saybolt seconds at 100 C. to aviscosity of 100 Saybolt seconds at 100 C. The purified still residue ismiscible with most organic liquids, including the petroleum distillateswith-. or sludge formation. Another important improvement in purifiedstill residue over the unpurified material is found after oxidation, inthat the purified material, as oxidized, is far more soluble than theoxidized unpurified material. By purifying the still residue I thereforenot only place it in better condition for use as a raw still residue,but as a matter of greater importance I prepare it for the production ofan oxidized product of improved solubility.

Whereas for many uses it is advantageous to retain and to oxidizesubstantially the entire initial content of the still residue(sulphates, sulphonates, and the like, being considered as whollyforeign bodies), for other purposes advantage is derived by removing aportion of the lower oily polymers of the still residue prior tooxidation.

If this topping operation by which a portion of the lower oily stillresidue polymers are removed is conducted in situ following the processof purification, the removal of a portion of the lower polymer oils maydistilling off the mineral spirits used in purifying' the still residue,and a continued distllaton which removes the initial solvent content,and naphthalene content of the still residue. Conducting suchdistillation to remove the oily lower boiling end of the still residue,that part of the distillation which is conducted at a temperature at andabove 425 F. is desirably conducted under vacuum and with the use oflive steam. If the still residue is purified at another time or place,or if purification of the still residuebe dispensed with, thedistillation to remove a portion of the oily lower boiling end of thestill residue 1.,is similarly conducted; distillation. being continueduntil the desired proportion of oily lower boiling end of the stillresidue has been distilled over, the distillation at and above 425 F.being desirably conducted under vacuum and in the follow sequentiallythe step of.

the solvent grade. This oily, lower boiling, end of the still residueconsists of the aromatic oils boiling up to about from 275 C. to 290 C.,and an oily substance formed of the dimers of the resin-forming. bodies(such as coumarone and indene) in the still residue, which boils fromabout 300 C. to about 360 C. It is this oily and of the still residuewhich possesses relatively high unsaturation, and which is, therefore,particularly susceptible to oxidation. As a precedent to an effectiveoxidizing treatment, it is necessary that some substantial proportion ofthe oily lower boiling end of the still residue be retained-asthat'portion of the still residue which is formed of higher polymerspossesses but relatively slight unsaturation, and material advantage isnot to be derived by attempted oxidation of it.

I have discovered that for certain purposes, and chiefiy for'use inlinoleum and mastic tile, a lesser elasticity than that obtained byoxidizing the total content of the still residue (disregarding foreignbodies, such as sulphonates, naphthaleneand solvents) is desirable. Whenthe entire true content of the still residue is oxidized into the stateof a solid'up to a desired melting-pointit has high penetration andelasticity. As an example, when the total true still residue is oxidizedto a melting-point of 180 F.,

it acquires a penetration of approximately 140- at 77 F. under a 50 gramload. As forming the body of tile of linoleum it then lacks firmnesssuillcient to support loads without yielding to a material extent. It issusceptible to penetration under concentrated forces, such as the. feetof articles of furniture at which a substantial weight load isconcentrated. For this purpose, therefore, I have found it desirable toremove a proportion of the oily lower end of the still-residue toprovide, upon adequate oxidation, a solid material of adequately highmelting-point and of moderate penetration and elasticity, so that asincorporated in tileor linoleum it may have adequate weight-supportingfirmness. As an exampie, the still residue, with about 70% oi its oilylower boiling end removed, when oxidized to a melting-point of 180 F.,acquires a penetration of only about 30 to 35 at 77 F. under a 50 gramload. In preparation for oxidation in contemplation oi? such use, theextent to which the still residue is topped will dependupon the type oftile or linoleum which is to be made from the oxidized product; that is,in accordance with the load-carrying firmness which may be necessary forit in its contemplated use and to theclimate in which the linoleum .ortile'is to be used.

Oxidation of the topped still residue may be conducted in accordancewith the disclosure-oi. my co-pending application Serial No. 53,213,filed December 6, 1935. Such procedure will be here summarized. Theliquid topped still residue is introduced into a vessel providedwithcoils for circulating steam, or other heating medium, and provided withperforated coils connected with a blower for introducing air underpressure. Desirably, the still residue is initially heated to atemperature approximating 175 F., in order to increase the fluidity ofthe material, and in order to facilitate the dispersion of air throughit. Air is then introduced in finely divided streams adjacent the bottomof the vessel, and is passed upwardly through the body of the stillresidue.

In so doing I introduce the air under such pres--.'

sure that it is capable, in a dispersed condition, of penetrating thebody of the liquid.

Blowing is continued for a total treating period and linoleum 3 to 4days, giving a melting-point of around 120 F., "is desirable. For use asan 3 days is desirable, while for use in making molded articles, and fortile and linoleum of grades adapted vfor heavy duty, a treatment of morethan 4 days to impart a melting-point of 150F. and over is useful.

Throughout the blowing the temperature of the still residue isprogressively raised, as it becomes possible so to do without blowingoiT content of the still residue-which it is desired to retain, and asit becomes necessary to do so in order to maintain the still residuesuiiiciently liquid for the dispersion of air therethrough. In

blown is not carried upwardly beyond about 325 F- With blowing carriedto any stage the result of the blowing is an oxidation of theunsaturates of the still residue, giving it drying qualities andoxidized untopped still residue and hard resinous material obtainable bydistilling oif all the lower polymers of the still residue, as well asthe initial naphthalene and solvent content of the still residue. Itspenetration and elasticity are substantially greater than the likequalities of a true resin, although less than those (of untoppedoxidized still residue.

Considering the purified and topped, but unoxidized, still residue, thisis a homogeneous material, free from curds. Its waterproofing qualitiesare improved. It is soluble in ordinary petroleum solvents, withoutsludge. Its viscosity, or melting-point, depends upon the stage to whichtopping is carried. It

and having a lesser elasticity than that resultant from oxidation 01'the total still residue content which comprises precipitatingsulphonates in the still residue by solvent separation in a low imatelytwice its volume of low-boiling aliphatic solvent, separating theprecipitated sulphonates from the solution of sulphonate-freed stillresidue in low-boiling aliphatic solvent, and by distillation separatingthe solvent from the still residue.

3. The herein described method of purifying raw aromatic still residuefrom the treatment of in the by-product ing and settling the raw still Ian equal volume of low-boiling aliphatic solvent,

separating the precipitated sulphonates from the boiling aliphaticsolvent, and by distillation separating thesolvent from the stillresidue.

4. The herein described method of purifying sulphonates of the

